Introduce SkVM Op::duplicate to localize visualization code

Change-Id: Ic343b1dcddb74d31c768afa67ab78955af418c9d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/483603
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Julia Lavrova <jlavrova@google.com>
3 files changed